Explosive.



UNITED STATES PATENT OFFICE."

OSWALD SILBERRAD, OF BUCKHURS T HILL, ENGLAND.

EXPLOSIVE.

No Drawing.

Specification of Letters Patent.

Patented Apr. 7, 1914.

Application filed June 3, 1912. Serial No. 701,242.

To all whom it may concern Be it known that I, OSWALD SILBERRAD, Ph. D., a subject of the King of Great Britain and Ireland,direct'or of the Silberrad Research Laboratories, and residing at Buckhurst Hill, in the county of Essex,

England, have invented certain new and sion and which remain liquid at ordinary temperatures.

According to this invention therefore, in the first place such an oily nitration product is produced by subjecting a coal-tar product of the kind referredto to nitration under suitable conditions. Such a nitration product can be produced from anyor all. or any liquid neutral fraction of the following tar products :viz., the oils boiling between about 200 to about 350 (3., that is to say, the liquid portions of middle, heavy and anthracene oils, the residues from the manufacture of carbolic acid, cresol, naphthalene and anthracene and also coal tar lubricating oil. In this connection I find that the 'high est fractions-i. e. the portion boiling from about 270 C. to about 350 O.do not so readily lend themselves to the treatment herein described, so that I prefer to utilize oils of which at least the greater portion boils'from 200-270 C.

The desired fraction or fractions is or are freed, if. necessary, from phenolic bodies,

bases and objectionable impurities, if any by washing with alkali and acid in the usual manner and in this way obtaining the new tral portion, the degree of importance of this chemical washing varying with the na-' ture and purity of the product required and of the fraction of tar oil to be dealt with.

- In order to effect nitration the tar oil as aforesaid, after having been submitted to such chemical washing as is desirable in the usual manner, is run into a mtratmg vessel fitted with an eflicient stirring apparatus and suitable cooling coils or jacket, and

brought into a state of violent agitation. The des1red amount of nitric acid is slowly run 1n, the temperature being carefully controlled by circulating water through the co ls or jacket, the mixture being violently agitated the entire time. After the full complement of nitric acid has been added sulfuric acid sufiicient to-cause the-completion of the reaction is run in, very special attention being directedto the efliciency ofthe agitation and to the control of the temperature throughout the whole operation.

The mixture is then allowed to stand over night, the oil separated, and washed with water and dilute sodium carbonatein the usual manner. I find-that the usual method of nitrating with mixed acids does not so readily lend itself to this operation, so that I prefer to employ the improved method above indicated according to which I obtain a mixture of the nitric acid and oil before adding the sulfuric acid. This is especially the case with regard to some fractions. advantage be applied to the nitration of hydrocarbons generally which give difiiculties in nitrationby the usual methods.

I In obtaining the oily nitration product according to one example I charge a suitable still with creosote oil containing. the residue from the manufacture of carbolic acid and naphthalene and collect that frac tion boiling from 200 to 270 After freeing the distillate from any naphthalene which separates out I-subject it to chemical washing with alkali and acid in the wellknown manner, using sufficient alkali to remove all phenolic bodies in the first place,

then water,-then sulfuric acid, then dilute alkali, and finally water again.

In efli'ecting the washing I find it convenient to subject the oil to a thorough washing with 2%% to 5% concentrated oil of vitriol and to repeat this operation until the desired degree of purity is obtained,

This method of nitration may with 2.5% to 20% of acid being used in this with agitator and cooling jacket. 68 lbs. of nitric acid (sp. gr. 1.50) are slowly .run in and finally 88 lbs. sulfuric acid- (sp. gr. 1.84:) gradually added. During the whole operation the contents of the vessel are kept in violent agitation and the temperature is kept at 20 to 35 C. After the full complement of acid has been added, the mixture is allowed to stand for about 16 hours, the nitrated oil is separated from acid and washed with waterand dilute soda carbonate in the usual manner. The product may be further purified if desired by distillation in cacao, though this operation needs care; the vacuum should be maintained as high as possible, and the temperature should not be allowed to rise much above 240 C.

,According to another method, the nitration may be carried out as follows: 1,000 parts by volume of oil, prepared as above boiling between 200 to 260 C. is run into a suitable nitration vessel fitted with agitator and cooling jacket. A mixture of 100 parts by volume of nitric acid of 1.5 sp. gr. with 25 parts of water is gradually run in. Then 100 parts by volume of nitric acid of sp. gr. 1.5 previously .diluted with 10 parts of water are gradually added. Then 100 parts by volume of nitric acid 1.5 sp. gr. previously diluted with 5 parts of water are gradually added. Then 100 parts by volume of nitric acid of 1.5 sp. gr. are gradually added, and finally 150 parts by volume of nitric acid of 1.5 sp.'gr. previously mixed with 450 parts by volume of concentrated sulfuric acid are gradually added. During the whole operation the contents of the vessel are kept under violent agitation and the temperature maintained preferably between 20 and 35 during addition of acid. The mixture is allowed to stand over night, and

is then gradually warmed to 60 to 70 C.-

under stirring.

It should be clearly understood that I do not confine myself to the limits of the examples given above, but may obtain suitable liquid neutral portions of coal-tar boiling between about 200 to 350 C. in any desired manner irrespective of the manner in which said tar has been produced from coal, and may nitrate such products in any suitable manner and to any desired extent, such that the product of nitration is essentially a liquid. Broadly I find that the greater the quantity of nitric acid used-,:-the more viscous will the finished product become.

' In'cases where very effective purification is required the following method may be adopted. The nitrated oil is first stirred with a weak solution say 5% of soda-ash,

preferably at-about 50 to C. for a period of about 12 to 24 hours. It is then separated, washed with water, and run into a suitable vessel containing clean water,

a few lumps of marble or the like are added, and the mixture gently boiled under the reflux condenser until all unstable compounds are decomposed. This is generally satisfactorily accom lished in from 24 to 48 hours.

Instead of soda-ash, I may use the carbonates or bicarbonates or hydrates of any of the alkali metals or mixtures containing any or all of these; similarly in place of marble I may use chalk, dolomite, magnesia or the carbonates or hydrates of any or all of the alkaline earths, or mixtures containing any of-these or any diific'ultly soluble compound capable of neutralizing the nitrous acids, produced from the gradual decomposition of the unstable products with preferably about 10 times its bulk, and also the production of bodies which are inert v as regards the nitrated product.

egarding the purification method above described it is to be observed that both it and its separate steps (2'. e. the washing with soda-ash or other substance on the one hand or the digestion with a suspension of a carbonate, hydrate or other body on the other) are of general application in the treatment of nitro compounds requiring special purification.

When nitro derivatives of the higher boiling fractions of coal tar referred to are purified by the process, I find that the product is not only rendered stable, but undergoes other changes. Thus the viscosity is altered, and the tendency to solidify is lessened, while the quantity of solid produced in the event of solidification occurring is reduced. 7

In carrying the invention into effect according to another example, where, for instance, the impurity consists essentially of a nitrosobody and the substance to be purified is required for the purpose of use in explosives, the nitro compound may be washed with water and run into a vessel containing clean water, preferably about ten times its bulk, and marble may be added and the mixture gently boiled under a reflux condenser until all unstable compounds are decom-' posed, the process occupying about 36 hours. Other insufliciently pure or mixed nitro compounds may be purified in a similar manner. The treatment is, therefore, of considerable importance when products are required for the manufacture of explosives, and especially of plastic explosives, as by means of the purification great stability, which is essential in such explosives, can be obtained By purification by means of carbonates or hydrates of the alkaline earths either with or without previous treatment with soda or the-like I find that the heat test of the product is considerably raised, whereas purified in the ordinary manner, nitrated products produced according to the process above described seldom show a heat test exceeding five minutes. Further, the tendency of the product to freeze and the consequent difliculty and danger of thawing is reduced.

The product or products of nitration of the coal tar fractions referred to are particularly suitable for use in the production of explosives and may be used for instance in blasting explosives either as the chief nitro compound therein or as a subsidiary ingredient. The fluidity of the nitro product referred to and its correspondingability to render other nitro compounds either fluid or more fluid is an important factor in facilitating the incorporation of the ingredient and particularl} in connection with the production of colloidal or plastic explosives.

Claims:

1. A process of preparing liquid diflicultly volatile nitro derivatives from coal tar consistin in separating from coal tar a neutral liqui portion of the oils boiling between about 200 C. to 350 C. and nitrating the same by the action of nitric. acid of suitable strength alone and then completing the nitration with nitric acid in the presence of sulfuric acid, as set forth.

2. A process of preparing liquid difli- I cultly volatile nitro derivatives from coal tar consisting in separating from coal tar a neutral liquid portion of the oils boiling between about 200 to 350 C. and nitrating the same by the action of successive quantities of nitric acid of increasing strength, finally completing the nitration with nitric acid in the presence of sulfuric acid, as 'set forth.

3. A process .of preparing liquid diflicultly volatile nitro derivatives from coal tar, consisting in separating from coaltar a portion of the oils boiling between 200 C. and 350 C., freeing said portion from phenolic and basic bodies, and nitrating the neutral liquid portion of oils boiling between 200 C. and 350 C. so obtained by successive quantities of nitric acid of increasing strength, and completing the nitration with nitric acid in presence of sulfuric acid, as set forth.

In testimony whereof I have signed my 7 name to this specification in the presence of two subscribing witnesses.

OSWALD SILBERRAD.

Witnesses:

HERBERT D. J AMESO'N, C. P. LIDDON. 

